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Homework Help: Potentiometer question

  1. Mar 8, 2005 #1
    I have a hw question about a potentiometer. There is a resistor between a and b that is a uniform wire of length l, with a sliding contact c at a distance x from b. An unknown potential difference V is measured by sliding the contact until the galvonometer G reads zero. I need to show that under this condition the unknown potential difference is given by V=(x/l)E. Any ideas???
  2. jcsd
  3. Mar 8, 2005 #2
    What is meant by E?
  4. Mar 8, 2005 #3
    E is the emf.
  5. Mar 8, 2005 #4
    The sliding contact divides the resistor in two other resistors [tex]R=R_1+R_2[/tex] where [tex]R_1[/tex] and [tex]R_2[/tex] are proportional with corresponding lengths (x and l-x). The current is given by
    and the potential difference between the ends of [tex]R_1[/tex]
    [tex]V=I\cdot R_1[/tex]
    and so on....
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